This disclosure relates generally to a device for reconditioning used cartridge cases, and more particularly, to a device for trimming a resized brass cartridge case to length, chamfering and deburring the fresh cut, and cleaning the case neck to prepare the case for reloading.
Brass cartridge cases elongate with repeated firing and resizing, and when the overall length exceeds that specified for the cartridge, the excess length must be trimmed away from the open end, or neck, of the case. For decades many attempts were made to improve and simplify case trimming to prepare metallic cartridges for reloading. In the art of case trimming, the devices either held the case stationary and turned the trimmer, or turned the case against a stationary trimmer.
Most of the devices were of the type that held the case stationary and turned the trimmer. These often resulted in the case neck being trimmed at a slight angle if the case were not held precisely straight by the device. To reduce the tendency to cut crookedly, such devices usually included either a pilot inserted into the case neck or a cylindrical die for holding the case body. The correct size pilot or die for each caliber of case was needed. Advocates of this type of trimming device had recommended turning the case half a turn and re-cutting after an initial trim, to attempt to partially straighten a crooked cut.
When a device cut the case mouth at an angle, and a bullet seated in that case was fired, it was released from the case neck at a slight angle to the bore, and engaged the rifling crookedly, diminishing accuracy. If a crooked case neck were crimped to the bullet, the crimp would bear unevenly on the bullet, further reducing accuracy of the fired bullet.
Fewer devices were designed to turn the case against a stationary trimmer. Some cases had a head that was not quite square with the body of the case. This was typically found in salvage military, or other cases, which had been fired by autoloading firearms or those with a bolt face not exactly square with the chamber. When such a case was held by its head and turned, the runout observed was called “wobble”.
Other causes of runout when a case was held by its head and turned were differences in the thickness of the brass case body or differences in annealing of the brass around the body. The thinner or softer side of the case stretched more on firing and contracted less on cooling than the thicker or harder side, resulting in a slight curve. Such cases were referred to as “banana” cases. Both wobble and banana were very small deviations from concentricity of a cartridge case and were not normally visible until a case was rotated by its head. Reloading press shell holders and resizing dies could only partially straighten such cases.
The effect of wobble and banana on trimmed cases was generally not found unless careful measurements of the mouth of the trimmed case were taken in several locations. Then the crooked mouth was found as a measureable difference from one side of the case to another.
Devices that held the case stationary either set case overall length correctly, from the head of the case, or from a less accurate datum on the shoulder of the case. This resulted in an incorrect case overall length if the resizing die set the shoulder at a different position than the specification for the cartridge. The user could adjust the trimmer and sizing die to meet the specification, but it was a tedious procedure that could spoil a few cases.
With some prior art devices the inside chamfering and outside deburring could also each be slightly crooked, decreasing the accuracy of fired bullets. The possibility of a crooked case mouth was greatly increased by those case preparation units having multiple tools revolving, where each case was brought to each spinning tool by hand. This inaccuracy was inherent to those devices because of the difficulty of manually bringing each case to a spinning tool precisely straight each time.
Prior art case preparation devices performed only one, or a few, of the steps required to trim and prepare cases for reloading, or took tedious adjustment, or produced inaccurate results. Many required each case to be repeatedly handled to perform each of the sequential steps. Most of the prior art devices were very fatiguing to operate if more than a few cases were prepared at one time. Shooters often wanted to prepare cases in batches of hundreds, so a solution was needed.